In this article you will learn How to create
custom exception in VB.NET.
Exception
Exceptions are the occurrence of some condition that changes the normal flow of
execution .
For example:
your program run out of memory , file does not exist in the
given path , network connections are dropped etc. More specifically for better
understanding , we can say it as Runtime Errors .
The
Concept
The whole idea of having customized Exception Handling is centered around the
fact that there needs to be a generic approach of catching and throwing
Exceptions.
For implementing custom Exception Handling we need to derive the class
CustomException from the system base class ApplicationException. In general, for
customizing Exception Handling the following components are necessary:
1. A custom exception class which would host the exception thrown and can be
thrown as a new exception.
2. A message class that would host all user - friendly Application messages that
need to be displayed.
Creating Custom Exception
VB.NET define your own custom exceptions to
identify the occurrence of unexpected events in your code.exceptions are
implemented in VB.Net as classes and objects.
-
Create a exception kind of class and inherit it from Exception class.
-
Override the Message property and ToString() method.
For example:
Module Module1
Class
NotEnoughBalanceException
Inherits Exception
Public Overrides ReadOnly Property
Message() As String
Get
Return "Sorry! Not
Engouh Balance"
End Get
End Property
End Class
Class Customer
Private name As String
Private balance As Integer
Public Sub New(ByVal name
As String,
ByVal opamt As Integer)
Me.name = name
Me.balance = opamt
End Sub
Public Sub
Deposit(ByVal amount As Integer)
balance +=
amount
End Sub
Public Sub
Withdraw(ByVal amount
As Integer)
If amount > balance
Then
Throw New NotEnoughBalanceException()
End If
balance -=
amount
End Sub
Public Sub
ShowBalance()
Console.WriteLine("Balance
of {0} is {1}", name, balance)
End Sub
End Class
Class ExpTest
Public Shared Sub Main()
Dim c As New Customer("Amit",
5000)
Try
c.Deposit(4000)
c.ShowBalance()
c.Withdraw(20000)
c.ShowBalance()
Catch ex As NotEnoughBalanceException
Console.WriteLine(ex.Message)
End Try
End Sub
End Class
End Module
OUTPUT:
Conclusion:
Hope this article would have helped you in understanding custom exception handling in VB.NET.